Most communication systems employing, for example, cellular telephones, require a series of ground station terminals that relay signals to and from satellite systems. The ground station terminals are necessary to boost the signal to the satellite antenna, since most satellite systems have relatively small antennas.
Large satellite antenna structures mounted on spacecraft can reduce or eliminate the signal boost requirement for the ground station terminals, thus reducing or eliminating the need for ground station terminals when using cellular telephones. Accordingly, the deployment of large antenna structures on spacecraft is becoming an increasingly desired occurrence.
Most large structures, including antenna structures, when deployed from a spacecraft have many operational requirements which must be met in order to successfully deploy the structure. For example, it is typically desired to hold the spacecraft at certain orientations during various stages of the deployment. However, the environmental torques and the reaction torques from deploying large structures cause significant attitude perturbation during the deployment process.
Generally, the size, the flexibility, and the time-varying characteristics of the large structure being deployed impose tremendous challenges to the dynamic modeling.
It is well established that proper dynamic modeling is the basis for all successful design programs, especially programs involving deployment of structures on a spacecraft. Only after successful testing on a high-fidelity dynamic model can one have confidence that a design will work in-flight. Thus, “how” to generate a high-fidelity model is an extremely important issue in the control design and analysis of deployment of large structures on the spacecraft.
An antenna structure may be made of numerous truss members, meshes and other components. Because of the relatively large number of components, it is essentially impossible to model an antenna as a multi-body system that includes all of the components due to the tremendous computational burden.
To this point, the traditional approach to model the time-varying mass properties of the large structure deployments on spacecraft has been the concept of “point-mass-on-sliders moving radially outward.” However, this approach provides a low accuracy result, and is therefore not an acceptable approach.
As a result, there is a need for an innovative dynamic modeling technique, which can provide a high-fidelity model and also relieve the computational burden significantly.